Liquid-sealed vibration control device

Abstract

In a hydraulic style vibration-proof device, a lower attachment fitting ( 34 ) forming an air chamber ( 36 ) between a diaphragm ( 16 ) and itself is fabricated of aluminum and is provided at its bottom wall portion with a through-hole ( 50 ), and a bolt ( 52 ) having a serration portion ( 54 ) below its head is press fitted in and secured to the through-hole, thereby fixedly providing the bolt ( 52 ) without involving a large projection into the air chamber ( 36 ) and at a low cost Further, the bottom wall portion ( 34 B) is formed to be thicker than a peripheral wall portion ( 34 C) of the lower attachment fitting and both are interconnected by a curved portion ( 34 D), thereby achieving an increase in strength.

1. A hydraulic style vibration-proof device comprising:
 a cylindrical fitting; 
 a first attachment fitting; 
 a vibration-isolating base made of rubber elastomer coupling an upper end opening of the cylindrical fitting and the first attachment fitting; 
 a diaphragm disposed to oppose the vibration-isolating base and forming a liquid chamber between the vibration-isolating base and the diaphragm within the cylindrical fitting; 
 and a cup-shaped second attachment fitting disposed below said diaphragm and attached to a lower end opening of the cylindrical fitting, forming an air chamber between the second attachment fitting and the diaphragm, 
 wherein said second attachment fitting is fabricated from aluminum and includes a peripheral wall portion, a bottom wall portion formed to be thicker in wall thickness than the peripheral wall portion and a curved portion interposed between the bottom wall portion and the peripheral wall portion and curved in an arc form in axial cross-section; 
 wherein the bottom wall portion is defined with a through-hole and has a bolt having a serration portion below its head press-fitted in the through-hole and provided fixedly to the second attachment fitting in such a manner that the bolt juts out from the second attachment fitting downwardly, 
 wherein a thickness of the second attachment fitting is gradually increased from the bottom wall portion toward the curved portion until reaching a maximum at the curved portion and then gradually decreased to the peripheral wall portio, and 
 wherein a plane of the upper end opening of the second attachment fitting slants relative to the bottom wall portion in a manner such that the peripheral wall portion is formed at different heights in the circumferential direction and at a higher location of the peripheral wall portion, a thickness at a corresponding location of the curved portion is thicker. 
 
   
   
     2. The hydraulic style vibration-proof device as set forth in  claim 1 , wherein a sealing agent is filled between the bolt and the second attachment fitting. 
   
   
     3. The hydraulic style vibration-proof device as set forth in  claim 1 , wherein an inner wall surface of the through-hole is, at its lower end, provided with a non-serration bonding portion between the inner wall surface and the bolt. 
   
   
     4. The hydraulic style vibration-proof device as set forth in  claim 3 , wherein a length of the serration portion is set to be shorter than a depth of the through-hole, thus providing the non-serration bonding portion between the serration portion and a lower end opening face of the through-hole. 
   
   
     5. The hydraulic style vibration-proof device as set forth in  claim 3 , wherein the lower end opening face of the through-hole is chamfered at its edge to provide the non-serration bonding portion. 
   
   
     6. The hydraulic style vibration-proof device as set forth in  claim 1 , wherein a bonding index d of the bolt is defined by the formula given below:
     d =( a/b )× c    
 wherein an outside diameter of the serration portion is a (mm), an aperture diameter of the through-hole is b (mm) and an axial length of a bonding portion of the serration portion to the through-hole is c (mm), and 
 wherein the bonding index d of the bolt is at least 3. 
 
   
   
     7. The hydraulic style vibration-proof device as set forth in  claim 6 , wherein the bonding index d of the bolt is at least 5.